The invention relates to a belt reel for a belt retractor of a vehicle occupant restraint system.
A belt reel for a seat belt retractor comprises a cylindrical spool for a belt webbing as well as at least one collar arranged at an axial end of the spool.
Typically, the belt reel is connected to a coiling spring which biases the belt reel in the winding direction of the belt webbing. Under normal operating circumstances the belt webbing can be freely withdrawn from the belt retractor against the force of the coiling spring, whereas when a webbing-sensitive or vehicle-sensitive locking mechanism is activated the belt reel is blocked so that the belt webbing cannot be withdrawn any further from the belt retractor. In this condition tensile forces in the belt webbing resulting from deceleration forces acting on a vehicle occupant in a possible collision are directed via the belt reel and the belt retractor into the vehicle. This is why the belt reel needs to be dimensioned such that it withstands the forces occurring in such a case under all circumstances. At the same time the intention is to dimension the belt reel as small as possible to enhance the capacity for receiving the belt webbing.
Belt reels are known hitherto from prior art which are either configured as a die-cast component or consist of a plastic-jacketed steel axle. Such designs are, however, a disadvantage both as regards their cost and their weight.
It is thus the object of the invention to provide a belt reel for a belt retractor which can be manufactured significantly cheaper and is less heavy.
This object is achieved with a belt reel for a belt retractor of a vehicle occupant restraint system, which comprises a cylindrical spool adapted for accommodation of a belt webbing and at least a first collar arranged at a first axial end of the spool. The spool consists of at least one sheet-metal sleeve, and the collar is formed by a sheet-metal disk. Despite sheet metal being used as the material for the belt reel a surprisingly high strength can be achieved since the basic shapes used, i.e. a sleeve and a disk, have a very high strength with regard to the loads acting on them. Accordingly, despite a low material expenditure the necessary high strength materialises for a very low weight. On top of this, sheet metal is relatively simple to work or shape, this in turn resulting in low production costs.
In accordance with a preferred embodiment of the invention it is provided for that the collar and the spool are configured integrally with each other. In this configuration the belt reel, preferably comprising a collar at each axial end, can be produced starting from a tube section, the axial ends of which are widened such that they each finally form a collar at the axial end of the belt reel. The spool is formed by the non-shaped section between the two axial ends of the tube section. Since all parts are configured integrally with each other a particularly high strength materialises whilst at the same time necessitating merely one low-cost step in forming the belt reel.
In accordance with another preferred embodiment it is provided for that the spool consists of two telescoped sheet-metal sleeves. Each of the sheet-metal sleeves is provided at one of its axial ends with the collar, produced, for example, by shaping an axial end of the tube section. Since the spool consists of two sheet-metal sleeves it features an even higher strength. When, in addition, as provided for in accordance with a further preferred embodiment, at least the outer of the two sheet-metal sleeves comprises a slot for passage of the belt webbing, then the belt webbing can be clamped between the two sheet-metal sleeves by simple ways and means. This minimises the expense of reliably defining the belt webbing on the belt reel.
Advantageous aspects of the invention read from the sub-claims.